The semiconductor integrated circuit (IC) industry has experienced rapid growth. Technological advances in IC materials and design have produced generations of ICs where each generation has smaller and more complex circuits than the previous generation. However, these advances have increased the complexity of processing and manufacturing ICs and, for these advances to be realized, similar developments in IC processing and manufacturing are needed. In the course of integrated circuit evolution, functional density (i.e., the number of interconnected devices per chip area) has generally increased while geometry size (i.e., the smallest component (or line) that can be created using a fabrication process) has decreased.
ICs may contain transistor devices that have doped regions. As transistor sizes continue to shrink, it is more difficult to prevent undesirable out-diffusion of the doped regions. Such out-diffusion may interfere with transistor device operation and/or degrade transistor performance. In addition, the shrinking transistor sizes may lead to problems such as current crowding, high source/drain resistance, and non-optimal doping profile.
Therefore, while existing methods of fabricating semiconductor devices have been generally adequate for their intended purposes, they have not been entirely satisfactory in every aspect.